This invention relates to a lens machining apparatus and lens machining method which machines the circumferential edges of lenses being machined to prescribed shapes for the purpose of inserting eyeglass lenses or other lenses being machined into lens frames.
For this type of lens machining apparatus, conventionally, a grindstone type lens machining apparatus has been used wherewith the lens circumferential edge is machined into the prescribed shape by grinding (edging) the circumferential surface of the lens with a grindstone. Insofar as plastic lenses are concerned, however, it is possible to do this by edging and machining. More recently, therefore, edging (cutting) type lens machining apparatuses have been developed wherewith the lens circumferential surface is edged (cut) with a cutter. This type of edging lens machining apparatus is disclosed in Japanese Patent Application Laid-Open No. H9-309051/1997 (published) and Japanese Patent Application Laid-Open No. H11-028650/1999 (published), for example. In Japanese Patent Application Laid-Open No. H4-315563/1992 (published) and Japanese Patent Application Laid-Open No. H5-4156/1993 (published), moreover, technology is disclosed for setting and altering the grinding (edging) load on the grindstone according to the lens circumferential edge thickness, with the object.of preventing lens cracking and efficiently performing suitable machining in cases where the circumferential surface of a lens is ground (edged) with a grindstone (revolving machining tool for machining circumferential surfaces).and the lens circumferential edge is machined to a prescribed shape.
However, with the edging type lens machining apparatus described in Japanese Patent Application Laid open No. H9-309051/1997 (published) and Japanese Patent Application Laid-Open No. H11-028650/1999 (published), executing the entire machining menu demanded for eyeglass lenses with a single chuck operation in one apparatus (where a single chuck operation means one lens holding operation wherewith there is no movement of a lens between different apparatuses) is something that still cannot be done. More specifically, in an ordinary eyeglass lens machining menu,
(1) lens circumferential surface edging and machining (inclusive of bevel edging)
(2) machining for forming grooves in lens circumferential surfaces, and
(3) chamfering edges where the lens circumferential surface and lens faces intersect
are included, but it has not been possible to handle all of these menu items with one chuck operation in one apparatus. In particular, because high machining precision is demanded in bevel edging, groove machining, and chamfering, the ideal is to be able to do this with one chuck operation, inclusive of measuring the shape and position of the lens being machined, but art wherewith that can be done has not been available. Nor has it always been possible, merely by setting and altering the grindstone grinding (edging) load according to the lens circumferential thickness, as in the art described in Japanese Patent Application Laid-Open No. H4-315563/1992 (published) and H5-4156/1993 (published), to perform machining of good precision or machining exhibiting good finished surfaces.
An object of the present invention, in view of the situation described in the foregoing, is to provide a lens machining apparatus and lens machining method wherewith the machining demanded for eyeglass lenses, from measurement to various machining items, can be accomplished with a single chuck operation, and wherewith it is possible to realize high-precision machining.
A first invention is a lens machining apparatus which machines the circumferential edge of a lens being machined for use in spectacles according to shape data, comprising: a lens holding unit which holds the lens being machined at the center of the lens and rotates the held lens being machined about the center of the lens; a circumferential surface edging and machining apparatus which edges the circumferential surface of the lens being machined that is held in the lens holding unit to a prescribed cross-sectional shape by a revolving edging tool; a groove machining apparatus which machines a groove in the circumferential surface of the lens being machined that is being held in the lens holding unit and that has been subjected to circumferential surface edging by the circumferential surface edging and machining apparatus; a chamfering apparatus which chamfers the edges where the circumferential surface and lens faces intersect in the lens being machined that is being held in the lens holding unit and that has been subjected to circumferential surface edging by the circumferential surface edging and machining apparatus; and a lens shape measurement apparatus which measures the lens surface shape and the lens surface position of the lens being machined being held in the lens holding unit.
With this apparatus, for the lens being machined held in the lens holding unit, lens circumference surface edging and machining can be rendered by the circumferential surface edging and machining apparatus, a groove can be machined in the circumferential surface of the lens by the groove machining apparatus, and the circumferential surface edges of the lens can be chamfered by the chamfering apparatus. Not only so, but the lens surface shape and lens surface position of the lens being machined held by the lens holding unit in the same manner can be measured by the lens shape measurement apparatus. Accordingly, by measuring the lens shape and position with the lens being machined still held with the same chuck, when bevel edging is required, bevels can be formed with good precision by circumferential surface edging, and when groove machining is required, a groove can be formed in the lens circumferential surface with good precision. Furthermore, in cases where chamfering is performed also, chamfered bevels can be formed with good precision in lens circumferential surface edges based on the measurement data and the machining particulars.
When provision is made for edging and machining the circumferential surface of a lens with a revolving edging tool, as in the present invention, furthermore, as compared to edging with a grindstone, the amount of edging in can be freely set, wherefore the process up to and including the finished shape can be freely controlled. For example, goal settings can be freely implemented, such as setting how many times to rotate the lens in performing everything up to finishing, or setting the number of seconds in which the machining is to be concluded.
A second invention is the first invention, comprising a machining action mechanism wherein the circumferential surface edging and machining apparatus, the groove machining apparatus, and the chamfering apparatus are deployed fixedly, which subjects the held lens being machined to machining actions by moving the lens holding unit relative to those machining apparatuses.
With this apparatus, the machining apparatuses are caused to perform machining actions by moving the lens being machined itself relative to the tools of the machining apparatuses. Accordingly, the machining apparatuses themselves need do nothing more than turn the tools, and the apparatus configuration is made simple.
A third invention is either the first or the second invention, wherein: the circumferential surface edging and machining apparatus and the groove machining apparatus are deployed adjacently on a base; the axis of the revolving tool of the groove machining apparatus is deployed in a direction perpendicular to the lens holding shaft of the lens holding unit and oriented in a direction parallel to the base; and the axis of the revolving tool of the groove machining apparatus, the axis of the revolving edging tool of the circumferential surface edging and machining apparatus, and the axis of the lens holding shaft are deployed at the same height.
With this apparatus, not only are the circumferential surface edging and machining apparatus and the groove machining apparatus deployed adjacently, but the axes thereof are aligned at the height of the axis of the lens holding shaft, wherefore a compact machining apparatus can be realized.
A fourth invention is any of the first to third inventions, wherein: the lens holding unit comprises a lens holding shaft and a lens pressing shaft; a lens holder receptacle which mounts the lens being machined is provided at the forward end of the lens holding shaft; the lens pressing shaft itself is deployed coaxially with the lens holding shaft, attached so that it can slide in the lens holding shaft direction by an arm unit; the lens pressing shaft, acted on by pressure from an air cylinder, moves to the lensholding shaft side, and presses the lens being machined by the lens presser oft he forward end thereof to the lens holding shaft side, whereby the lens being machined is held sandwiched between the lens holding shaft and the lens pressing shaft.
With th is apparatus, air is used as the source of the drive for obtaining a lens holding force, and the lens holding force (so-called chuck pressure) can be freely adjusted by changing the pressure setting in a regulator.
A fifth invention is any of the first to fourth inventions, wherein both the groove machining apparatus and the chamfering apparatus are configured by a common ball end mill.
With this invention, groove machining and chamfering are done with an end mill of small diameter used for groove edging. Therefore, compared to machining done with a conventional grindstone, small chamfered bevels can be accurately finished with little interference with other places. Also, because a single end mill is used for both groove edging and chamfering, the number of tools can be decreased, which contributes to cost reduction. Also, because groove edging and chamfering machining can be done in more or less immediate succession with a single chuck operation, machining time can be reduced. Furthermore, because a single drive system suffices due to the employment of one tool for different uses, the apparatus can be made smaller and costs reduced. And, because the number of tools is not increased, tool management is also made easy.
A sixth invention is a lens machining method wherein: a lens being machined for use in spectacles is held at the center of the lens, the circumferential surface of the held lens being machined is edged by a revolving machining tool for circumferential surface machining, the circumferential surface is edged about the entire circumference of the lens being machined by causing the lens being machined to revolve about the center of the lens, and a lens having a prescribed circumferential edge shape is thereby machined; the lens being machined is held by a lens holding unit; and lens circumferential surface edging and machining inclusive of bevel edging, machining to edge a groove in the lens circumferential surface, and chamfering the edges where the lens circumferential surface and the lens faces intersect are performed with the holding condition implemented by the lens holding unit maintained as it is.
This is a method that executes the entire machining menu demanded for eyeglass lenses with a single chuck operation in one apparatus (where a single chuck operation means one lens holding operation wherewith there is no movement of the lens between different apparatuses). In other words, machining wherein particularly high machining precision is required, such as bevel edging, groove edging, and chamfering, is performed with a single chuck operation, so that it is possible to do such machining with higher precision than in the conventional case where it is necessary to recheck the work for every machining process.
A seventh and an eighth invention are lens machining methods wherein: a lens being machined for use in spectacles is held at the center of the lens, the circumferential surface of the held lens being machined is edged by a revolving machining tool for circumferential surface machining, the circumferential surface is edged about the entire circumference of the lens being machined by causing the lens being machined to revolve about the center of the lens, and a lens having a prescribed circumferential edge shape is thereby machined; and at least one or other of the turning speed of the revolving machining tool for circumferential surface edging, the turning speed of the lens being machined when it is revolving, and the number of revolutions of the lens being machined for edging away a prescribed amount of material is set and altered according to either the material type or the lens circumferential edge thickness of the lens being machined.
In some cases the revolving machining tool for the circumferential surface machining is a cutter for performing edging with a cutting blade provided at the outer periphery of the circumferential surface of the lens being machined.
In the case of a plastic lens, for example, there are both soft materials and hard materials. And in the case of an eyeglass lens, the lens circumferential edge thickness (edge thickness) differs according to the power. When such is machined under uniform machining conditions, the machining load will naturally be different depending on the hardness of the material and the lens circumferential edge thickness. Therefore, not only will the machining precision vary according to machining load differences, but there is a possibility that machining efficiency will also be affected. That being so, in the seventh to ninth inventions, provision is made for setting and altering the machining conditions according to the material and the lens circumferential edge thickness.
The machining conditions in such cases include the turning speed of the cutter, grindstone, or other revolving machining tool for circumferential surface edging, the turning speed when the lens being machined is revolving, and the number of revolutions in the lens being machined for edging away a prescribed amount of material. By setting and altering at least one of these parameters, the machining conditions can be made more appropriate.
In the case of an eyeglass lens, for example, as the final finished shape is approached, the lens circumferential edge shape will cease to be circular, wherefore the moving radial (radius) from the center of turning to the machining point (that is, the point where the tool is made to interfere with the lens and actually edge away the lens) will vary according to the turning angle of the lens being machined. Thereupon, the angular velocity of the lens when turning is controlled to make the circumferential speed of the machining point caused by the lens turning to be uniform. By so doing, the speed of movement of the lens (that is, the speed of movement of the machining point) relative to the tool will become the same, and the entire circumference can be machined under more or less the same conditions.
Furthermore, by varying the turning speed of the revolving machining tool itself according to the movement of the machining point, without varying the lens turning angle speed, the entire circumference can be machined under more or less the same conditions.
A tenth invention is a lens machining method wherein: a lens being machined is caused to revolve about the center of the lens while applying a revolving groove tool to the circumferential surface of the lens being machined that has been machined to a prescribed circumferential edge shape, whereby a groove is formed in the circumferential surface of the lens being machined; and at least one or other of the turning speed of the revolving groove tool and the turning speed when the lens being machined is revolving is set and altered according to the material of the lens being machined.
An 11th invention is a lens machining method wherein: a lens being machined is caused to revolve about the center of the lens while applying a revolving chamfering tool to the edges where the lens faces and the circumferential surface of the lens being machined that has been machined to a prescribed circumferential edge shape intersect, whereby the edges are chamfered; and at least one or other of the turning speed of the chamfering tool and the turning speed when the lens being machined is revolving is set and altered according to the material of the lens being machined.
Groove edging and chamfering are not machining processes which edge away a large amount of material, wherefore the machining may be completed by causing the lens to revolve only one time. That being so, although the number of lens revolutions was added as a settable and alterable parameter for the case of circumferential surface machining, here that factor is removed from the parameters. Furthermore, because neither groove edging nor chamfering is a machining item wherein the machining load is influenced by differences in the lens circumferential edge thickness, lens circumferential edge thickness is also eliminated from the machining conditions. Thereupon, only the material of the lens being machined is left as a condition, and, in terms of parameters, provision is made for setting and altering the turning speed of the revolving groove tool or chamfering tool, and the turning speed when the lens being machined is revolving.
Thus, by setting and altering at least one of two parameters, according to the material of the lens being machined, the machining conditions can be made more appropriate.
A 12th invention is a lens machining method wherein: a lens being machined is held by the center of the lens, the circumferential surface of the held lens being machined is edged away by a revolving machining tool for circumferential surface machining, and the lens being machined is caused to revolve about the center of the lens, whereby the circumferential surface is edged away about the entire circumference of the lens being machined, and the lens is thereby machined to a prescribed circumferential edge shape; and at least one or other of the turning speed of the revolving machining tool for edging the circumferential surface or the turning speed when the lens being machined is revolving is set and altered, when roughly machining the circumferential surface of the lens being machined, and when thereafter performing finishing machining.
A 13th invention is the 12th invention, wherein a cutter that edges the circumferential surface of the lens being machined with a cutting blade deployed at the outer circumference thereof is used as the revolving machining tool for circumferential surface machining.
A 14th invention is the 13th invention, wherein both rough machining and finishing machining are done with the same cutter.
Rough machining, in general, is the process of removing edging material up to the point where finishing machining is performed. Therefore, there is no need to elicit dimensional precision or finished surface precision, and it is better if the prescribed amount of edging material can be removed quickly. Thereupon, such is implemented by raising the feed speed (the turning speed wherewith the lens revolves) and/or setting the depth of edging to make it deeper. Here, in order to deepen the edging depth, the edging load may be made large in the case of edging with a grindstone, or the feed speed in the edging depth direction may be set higher in the case of edging with a cutter. Finishing machining, on the other hand, is a process where dimensional precision and finished surface precision are elicited, wherefore raising the turning speed of the grindstone or cutter or other revolving machining tool and/or lowering the feed speed is commonly practiced.
When such is done, in the case of circumferential surface edging with a cutter, both rough machining and finishing machining can be performed by changing the turning speed of the cutter.
A 15th invention is a lens measurement method wherein: in machining the circumferential edge of an eyeglass lens being machined according to lens frame shape data, a stylus is caused to make a trace on the lens face of the lens being machined that is held by a lens holding unit, according to the lens frame shape data, and the displacement of that stylus in the lens thickness dimension is detected, whereby the position on the lens face is measured; and positions on the lens face at points removed from the traced points are calculated using measurement data for the points traced by the stylus and lens design data inclusive of lens face information for the lens being machined previously given.
In the 15th invention, the lens design data includes complete coordinate data (lens face information) relating to the lens faces. Accordingly, if the stylus is made to trace the lens face according to the lens frame shape data in the condition wherein the lens is held and the position on the lens face is actually measured, based on that actually measured data and on separately given lens design data, positional data for any position on the lens face can be calculated. Accordingly, when bevel edging is being done, for example, by using computations to calculate positional data for the edges on both sides of the base of the bevel, and performing the bevel edging based on those data, the position of the bevel can be finished with good precision.
A 16th invention is the 15th invention, wherein the points removed away from the traced points are made the edges where the lens circumferential surface and the lens faces of the lens being machined intersect after circumferential surface finishing machining.
In the case of the 16th invention, because the points where the positions on the lens faces are sought are made the edges where the lens circumferential surface and the lens faces of the lens being machined intersect after circumferential surface finishing machining, in the case of bevel edging, for example, when the lens circumferential surface is groove machined, or when chamfering the edge, those can be finished with good precision.
A 17th invention is the 16th invention, wherein: the stylus is caused to trace the lens face at positions on an extended line in the direction of the lens holding shaft at the bevel apex when bevel edging the lens circumferential surface; and the points removed away from the traced points are made the edges at the intersections of the lens faces and the lens circumferential surface corresponding to the base of the bevel.
With the 17th invention, when doing bevel edging, positional data are acquired for the edges at the intersections of the lens faces and the lens circumferential surface corresponding to the base of the bevel, wherefore the position of the bevel can be finished with good precision based on the data for the edges at those intersections.
An 18th invention is any one of the 15th to 17th inventions, wherein a pair of styluses is used, and positions on the front and back lens faces are measured simultaneously by causing the front and back lens faces of the lens being machined to be traced.
With the 18th invention, because positions on the front and back lens faces are measured simultaneously with the pair of styluses, the edge thickness can be calculated from those data.
A 19th invention is a lens machining method wherein: a lens measurement method cited in any one of inventions 15 to 18 cited above is used; data on positions on the lens faces of the lens being machined are acquired; and the lens being machined is subjected to circumferential surface machining based on those data.
With the 19th invention, lens circumferential surface machining is performed on the bases of data acquired by a measurement method described earlier, wherefore the circumferential surface machining precision can be raised.
A 20th invention is the 19th invention, wherein a bevel is formed in the lens circumferential surface when performing the circumferential surface machining.
With the 20th invention, a bevel is formed on the circumferential surface of the lens on the basis of data acquired by a measurement method described earlier, wherefore the position of the bevel can be finished with good precision.
A 21st invention is the 19th invention, wherein, after the circumferential surface machining, a groove is machined in the circumferential surface using the acquired data.
With the 21st invention, a groove is formed in the circumferential surface of the lens on the basis of data acquired by a measurement method described earlier, wherefore the position of the groove can be finished with good precision.
A 22nd invention is any one of the 19th to 21st inventions, wherein, after the circumferential surface machining, the edges where the lens faces and the lens circumferential surface intersect are chamfered using the acquired data.
With the 22nd invention, the edges where the lens faces and the lens circumferential surface intersect are chamfered on the basis of data acquired by a measurement methods described earlier, wherefore the chamfered bevels can be finished with good precision.